A pinch valve generally differs from conventional valves in that, instead of having closing elements that interfere with a fluid flow, they apply pressure on a sleeve to prevent a flow. When in open position, no closing element is present within the sleeve and the flow is unimpeded by the presence of the valve. Pinch valves are frequently used in applications where solid or semi-solid material, such as powder, granules, pellets, fibers or similar material, flow within the sleeve. They may be used in soft applications, such as for example in waste water plants, or in heavy industrial applications.
Conventional mechanical pinch valves apply pressure using a movable closure bar at one point of a circumference of the sleeve, for example at the top of the circumference, flattening the sleeve towards a fixed bottom, thereby greatly deforming the sleeve. Some pinch valves use air pressure for flattening the sleeve.
In any case, a sleeve on which pressure is repeatedly applied by a pinch valve may lose flexibility and crack or otherwise break, as a result of multiple opening and closing cycles. Use of pinch valves, especially mechanical pinch valves, oftentimes requires maintenance for sleeve replacement. Such maintenance implies downtime as the pinch valve may need to be dismounted from a site, moved to a workshop and opened with tools in order to allow changing of the sleeve. Manpower costs and loss of income due to plant downtime may be important.
Therefore, there is a need for a pinch valve that meets requirements of a broad range of applications while providing ease of maintenance.